1. Technical Field
The present invention relates to a robot system.
2. Related Art
In related art, robot systems for robots to pick up works (objects) and arrange the works in predetermined positions and poses have been developed. In the robot system, when the object is picked up, the object is detected by pattern matching between the shape of the object and a shape of a target shown by a model registered in advance.
For example, an image processing apparatus disclosed in Patent Document 1 (JP-A-2010-97436) uses a pattern model corresponding to a registered image registered in advance for searching for a search object similar to the registered image from a search object image and performs positioning. Further, in generation of a model, a plurality of objects are captured and captured images are acquired in advance, and an image of one arbitrary object of the plurality of objects is selected. The image of the selected one object can be used for pattern matching processing.
However, pattern matching processing between the shape of the target according to the generated model and the object to be worked can be unsuccessful by the following causes.
(1) Changes in shadow cast: When an object having a solid shape is irradiated with light, a shadow as a part in which the light is blocked by the object is formed around the object. Accordingly, shadow cast changes in response to changes of a light source (e.g., illumination, environment light, or the like) and changes in position and pose relationships between the light source and the object. Even when the light source is unchanged, the shadow cast changes in response to the position and pose of the object placed within a field of view of an imaging apparatus.
(2) Changes in pose of object having solid shape: An object placed within a field of view of an imaging apparatus has a solid shape, and its planar shape differs depending on its pose. Further, even when poses of objects are the same, apparent contour shapes differ depending on a difference in position within the field of view. Particularly, in an imaging apparatus including a wide lens, the shape difference clearly appears between an object placed on an optical axis and an object having the same solid shape placed on the periphery of the field of view.
(3) Changes in texture of object, changes in texture due to reflection by object surface: a texture (pattern) on a surface of an object apparently changes because the position within the field of view of the imaging apparatus differs depending on its part. Further, a glossy object reflects arriving light, and its pattern apparently changes depending on the amount of light or the arriving direction. Furthermore, for example, even objects having the same shape and size like prints of best-before dates attached to wrappings of foods may have parts individually different in appearance.
(4) Existence of surrounding objects: In pattern matching processing, images representing targets are registered as models. In this regard, a registered area (window) may contain images of other objects than the targets.